The Overall objective of this work will continue to be the improvement of immunization against cholera by the development of more effective immunizing procedures and the study of the mode of action of antibacterial and antitoxic immunity. Further study is planned on the primary and secondary structure of cholera toxin and the relationships of structure to function. Toxin modification studies will be oriented towards development of superior toxoids. Local and systemic antibody responses will continue to be studied in man and in experimental animals. Protection afforded by immunization will be evaluated in experimental animals by intestinal challenge with V. cholerae. BIBLIOGRAPHIC REFERENCES: Peterson, J. W. and W. F. Verwey. 1974. Radiolabeled toxin for studying binding of cholera toxin and toxoids to intestinal mucosal receptor sites. Proc. Soc. Exper. Biol. Med. 145:1187-1191. Peterson, J. W. 1974. Tissue binding properties of the cholera toxin. Infect. and Immun. 10:157-166.